Source code for google.auth.impersonated_credentials

# Copyright 2018 Google Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.

"""Google Cloud Impersonated credentials.

This module provides authentication for applications where local credentials
impersonates a remote service account using `IAM Credentials API`_.

This class can be used to impersonate a service account as long as the original
Credential object has the "Service Account Token Creator" role on the target
service account.

    .. _IAM Credentials API:

import base64
import copy
from datetime import datetime
import json

import six
from six.moves import http_client

from google.auth import _helpers
from google.auth import credentials
from google.auth import exceptions
from google.auth import jwt
from google.auth.transport.requests import AuthorizedSession

_DEFAULT_TOKEN_LIFETIME_SECS = 3600  # 1 hour in seconds

_IAM_SCOPE = [""]

    + "/serviceAccounts/{}:generateAccessToken"

    + "/serviceAccounts/{}:signBlob"

    + "projects/-/serviceAccounts/{}:generateIdToken"

_REFRESH_ERROR = "Unable to acquire impersonated credentials"

_DEFAULT_TOKEN_LIFETIME_SECS = 3600  # 1 hour in seconds


def _make_iam_token_request(
    request, principal, headers, body, iam_endpoint_override=None
    """Makes a request to the Google Cloud IAM service for an access token.
        request (Request): The Request object to use.
        principal (str): The principal to request an access token for.
        headers (Mapping[str, str]): Map of headers to transmit.
        body (Mapping[str, str]): JSON Payload body for the iamcredentials
            API call.
        iam_endpoint_override (Optiona[str]): The full IAM endpoint override
            with the target_principal embedded. This is useful when supporting
            impersonation with regional endpoints.

        google.auth.exceptions.TransportError: Raised if there is an underlying
            HTTP connection error
        google.auth.exceptions.RefreshError: Raised if the impersonated
            credentials are not available.  Common reasons are
            `` is not enabled or the
            `Service Account Token Creator` is not assigned
    iam_endpoint = iam_endpoint_override or _IAM_ENDPOINT.format(principal)

    body = json.dumps(body).encode("utf-8")

    response = request(url=iam_endpoint, method="POST", headers=headers, body=body)

    # support both string and bytes type
    response_body = ("utf-8")
        if hasattr(, "decode")

    if response.status != http_client.OK:
        exceptions.RefreshError(_REFRESH_ERROR, response_body)

        token_response = json.loads(response_body)
        token = token_response["accessToken"]
        expiry = datetime.strptime(token_response["expireTime"], "%Y-%m-%dT%H:%M:%SZ")

        return token, expiry

    except (KeyError, ValueError) as caught_exc:
        new_exc = exceptions.RefreshError(
            "{}: No access token or invalid expiration in response.".format(
        six.raise_from(new_exc, caught_exc)

[docs]class Credentials(credentials.CredentialsWithQuotaProject, credentials.Signing): """This module defines impersonated credentials which are essentially impersonated identities. Impersonated Credentials allows credentials issued to a user or service account to impersonate another. The target service account must grant the originating credential principal the `Service Account Token Creator`_ IAM role: For more information about Token Creator IAM role and IAMCredentials API, see `Creating Short-Lived Service Account Credentials`_. .. _Service Account Token Creator: .. _Creating Short-Lived Service Account Credentials: Usage: First grant source_credentials the `Service Account Token Creator` role on the target account to impersonate. In this example, the service account represented by svc_account.json has the token creator role on ``. Enable the IAMCredentials API on the source project: `gcloud services enable`. Initialize a source credential which does not have access to list bucket:: from google.oauth2 import service_account target_scopes = [ ''] source_credentials = ( service_account.Credentials.from_service_account_file( '/path/to/svc_account.json', scopes=target_scopes)) Now use the source credentials to acquire credentials to impersonate another service account:: from google.auth import impersonated_credentials target_credentials = impersonated_credentials.Credentials( source_credentials=source_credentials, target_principal='', target_scopes = target_scopes, lifetime=500) Resource access is granted:: client = storage.Client(credentials=target_credentials) buckets = client.list_buckets(project='your_project') for bucket in buckets: print( """ def __init__( self, source_credentials, target_principal, target_scopes, delegates=None, lifetime=_DEFAULT_TOKEN_LIFETIME_SECS, quota_project_id=None, iam_endpoint_override=None, ): """ Args: source_credentials (google.auth.Credentials): The source credential used as to acquire the impersonated credentials. target_principal (str): The service account to impersonate. target_scopes (Sequence[str]): Scopes to request during the authorization grant. delegates (Sequence[str]): The chained list of delegates required to grant the final access_token. If set, the sequence of identities must have "Service Account Token Creator" capability granted to the prceeding identity. For example, if set to [serviceAccountB, serviceAccountC], the source_credential must have the Token Creator role on serviceAccountB. serviceAccountB must have the Token Creator on serviceAccountC. Finally, C must have Token Creator on target_principal. If left unset, source_credential must have that role on target_principal. lifetime (int): Number of seconds the delegated credential should be valid for (upto 3600). quota_project_id (Optional[str]): The project ID used for quota and billing. This project may be different from the project used to create the credentials. iam_endpoint_override (Optiona[str]): The full IAM endpoint override with the target_principal embedded. This is useful when supporting impersonation with regional endpoints. """ super(Credentials, self).__init__() self._source_credentials = copy.copy(source_credentials) # Service account source credentials must have the _IAM_SCOPE # added to refresh correctly. User credentials cannot have # their original scopes modified. if isinstance(self._source_credentials, credentials.Scoped): self._source_credentials = self._source_credentials.with_scopes(_IAM_SCOPE) self._target_principal = target_principal self._target_scopes = target_scopes self._delegates = delegates self._lifetime = lifetime self.token = None self.expiry = _helpers.utcnow() self._quota_project_id = quota_project_id self._iam_endpoint_override = iam_endpoint_override
[docs] @_helpers.copy_docstring(credentials.Credentials) def refresh(self, request): self._update_token(request)
def _update_token(self, request): """Updates credentials with a new access_token representing the impersonated account. Args: request (google.auth.transport.requests.Request): Request object to use for refreshing credentials. """ # Refresh our source credentials if it is not valid. if not self._source_credentials.valid: self._source_credentials.refresh(request) body = { "delegates": self._delegates, "scope": self._target_scopes, "lifetime": str(self._lifetime) + "s", } headers = {"Content-Type": "application/json"} # Apply the source credentials authentication info. self._source_credentials.apply(headers) self.token, self.expiry = _make_iam_token_request( request=request, principal=self._target_principal, headers=headers, body=body, iam_endpoint_override=self._iam_endpoint_override, )
[docs] def sign_bytes(self, message): iam_sign_endpoint = _IAM_SIGN_ENDPOINT.format(self._target_principal) body = { "payload": base64.b64encode(message).decode("utf-8"), "delegates": self._delegates, } headers = {"Content-Type": "application/json"} authed_session = AuthorizedSession(self._source_credentials) response = url=iam_sign_endpoint, headers=headers, json=body ) return base64.b64decode(response.json()["signedBlob"])
@property def signer_email(self): return self._target_principal @property def service_account_email(self): return self._target_principal @property def signer(self): return self
[docs] @_helpers.copy_docstring(credentials.CredentialsWithQuotaProject) def with_quota_project(self, quota_project_id): return self.__class__( self._source_credentials, target_principal=self._target_principal, target_scopes=self._target_scopes, delegates=self._delegates, lifetime=self._lifetime, quota_project_id=quota_project_id, iam_endpoint_override=self._iam_endpoint_override, )
[docs]class IDTokenCredentials(credentials.CredentialsWithQuotaProject): """Open ID Connect ID Token-based service account credentials. """ def __init__( self, target_credentials, target_audience=None, include_email=False, quota_project_id=None, ): """ Args: target_credentials (google.auth.Credentials): The target credential used as to acquire the id tokens for. target_audience (string): Audience to issue the token for. include_email (bool): Include email in IdToken quota_project_id (Optional[str]): The project ID used for quota and billing. """ super(IDTokenCredentials, self).__init__() if not isinstance(target_credentials, Credentials): raise exceptions.GoogleAuthError( "Provided Credential must be " "impersonated_credentials" ) self._target_credentials = target_credentials self._target_audience = target_audience self._include_email = include_email self._quota_project_id = quota_project_id def from_credentials(self, target_credentials, target_audience=None): return self.__class__( target_credentials=self._target_credentials, target_audience=target_audience, include_email=self._include_email, quota_project_id=self._quota_project_id, ) def with_target_audience(self, target_audience): return self.__class__( target_credentials=self._target_credentials, target_audience=target_audience, include_email=self._include_email, quota_project_id=self._quota_project_id, ) def with_include_email(self, include_email): return self.__class__( target_credentials=self._target_credentials, target_audience=self._target_audience, include_email=include_email, quota_project_id=self._quota_project_id, )
[docs] @_helpers.copy_docstring(credentials.CredentialsWithQuotaProject) def with_quota_project(self, quota_project_id): return self.__class__( target_credentials=self._target_credentials, target_audience=self._target_audience, include_email=self._include_email, quota_project_id=quota_project_id, )
[docs] @_helpers.copy_docstring(credentials.Credentials) def refresh(self, request): iam_sign_endpoint = _IAM_IDTOKEN_ENDPOINT.format( self._target_credentials.signer_email ) body = { "audience": self._target_audience, "delegates": self._target_credentials._delegates, "includeEmail": self._include_email, } headers = {"Content-Type": "application/json"} authed_session = AuthorizedSession( self._target_credentials._source_credentials, auth_request=request ) response = url=iam_sign_endpoint, headers=headers, data=json.dumps(body).encode("utf-8"), ) id_token = response.json()["token"] self.token = id_token self.expiry = datetime.fromtimestamp(jwt.decode(id_token, verify=False)["exp"])